A coordinated attack by a radical Islamist sect in north Nigeria's largest city killed at least 143 people, a hospital official said Saturday, representing the extremist group's deadliest assault since beginning its campaign of terror in Africa's most populous nation.

Soldiers and police officers swarmed Kano's streets as Nigeria's president again promised the sect known as Boko Haram would "face the full wrath of the law." But the uniformed bodies of security agents that filled a Kano hospital mortuary again showed the sect can strike at will against the country's weak central government.

Friday's attacks hit police stations, immigration offices and the local headquarters of Nigeria's secret police in Kano, a city of more than 9 million people that remains an important political and religious center in the country's Muslim north. A suicide bomber detonated a car loaded with powerful explosives outside a regional police headquarters, tearing its roof away and blowing out windows in a blast felt miles away as its members escaped jail cells there.

Authorities largely refused to offer casualty statistics as mourners began claiming the bodies of their loved ones to bury before sundown, following Islamic tradition. However, a hospital official told The Associated Press at least 143 people were killed in the attack.

The official spoke on condition of anonymity because he wasn't authorized to release the death toll to journalists. The toll could still rise, since other bodies could be held at other clinics and hospitals in the sprawling city.

State authorities enforced a 24-hour curfew in the city, with many remaining home as soldiers and police patrolled the streets and setup roadblocks. Gunshots echoed through some areas of the city into Saturday morning.

Nwakpa O. Nwakpa, a spokesman for the Nigerian Red Cross, said volunteers offered first aid to the wounded, and evacuated those seriously injured to local hospitals. A survey of two hospitals by the Red Cross showed at least 50 people were injured in Friday's attack, he said.

A Boko Haram spokesman using the nom de guerre Abul-Qaqa claimed responsibility for the attacks in a message to journalists Friday. He said the attack came because the state government refused to release Boko Haram members held by the police.

"The full horror of last night's events is still unfolding, but we know that a great many people have died and many more have been injured," Hague said in a statement. "The nature of these attacks has sickened people around the world and I send my deepest condolences and sympathies to the families of those killed and to those injured."

The U.S. Embassy said it had canceled all staff travel to northern Nigeria after Friday's attacks.

President Goodluck Jonathan also condemned an attack he said saw innocent people "brutally and recklessly cut down by agents of terror."

"As a responsible government, we will not fold our hands and watch enemies of democracy, for that is what these mindless killers are, perpetrate unprecedented evil in our land," Jonathan said in a statement. "I want to reassure Nigerians ... that all those involved in that dastardly act would be made to face the full wrath of the law."

But Jonathan's government has repeatedly been unable to stop attacks by Boko Haram, whose name means "Western education is sacrilege" in the Hausa language of Nigeria's north. The group has carried out increasingly sophisticated and bloody attacks in its campaign to implement strict Shariah law and avenge the deaths of Muslims in communal violence across Nigeria, a multiethnic nation of more than 160 million people.

Authorities blamed Boko Haram for at least 510 killings last year alone, according to an AP count, including an August suicide bombing on the U.N. headquarters in the country's capital Abuja. So far this year, the group has been blamed for at least 219 killings, according to an AP count.

Boko Haram recently said it specifically would target Christians living in Nigeria's north, but Friday's attack saw its gunmen kill many Muslims. In a recent video posted to the Internet, Imam Abubakar Shekau, a Boko Harm leader, warned it would kill anyone who "betrays the religion" by being part of or sympathizing with Nigeria's government.

"I swear by Allah we will kill them and their killing will be nothing to us," Shekau said. "It will be like going to prayers at 5 a.m."

Friday's attacks also could cause more unrest, as violence in Kano has set off attacks throughout the north in the past, including postelection violence in April that saw 800 people killed. Kano, an ancient city, remains important in the history of Islam in Nigeria and has important religious figures there today.

Amid the recent unrest and attacks, at least two journalists have been killed in Nigeria. Journalist Enenche Akogwu, who worked as a correspondent in Kano for private news station Channels Television, was shot Friday while reporting on the attacks, colleagues said. In central Nigeria's city of Jos, Nansok Sallah, a news editor for a government-owned radio station called Highland FM, was found dead in a shallow stream Thursday, the victim of an apparent murder, the Committee to Protect Journalists said.